Efeitos do tempo de espera, temperatura de secagem e tempo de armazenamento sobre propriedades tecnológicas e compostos fenólicos de grãos de arroz com pericarpo vermelho

Abstract

Rice is one of the main cereals produced and consumed in Brazil and the world. Most of the grain grown belongs to the brown pericarp rice, but in the last years the demand of the consumers has been increased to the grains that present the pigmented pericarp due mainly to the health benefits provided by them. The rice is harvested with high humidity and drying is a key step in maintaining the quality and nutritional value of the product. The objective of this study was to evaluate the immediate and latent effects caused by the waiting time for drying (immediate, 3 and 6 days), as well as the material storage temperature during the waiting period (15 ° and 25 ° C) on the main indicators of product quality stored for 12 months. The results of this first study show that the colorimetric profile of the grains undergoes significant changes as a consequence of the variations caused by the waiting time for drying in phenolic compounds and proanthocyanidins. The chemical, physical, industrial and cooking properties of the grains are also negatively altered due to the waiting time, but the cooling of the mass attenuates its effects. A second study aimed at evaluating the immediate and latent effects of temperature (40 °, 60 °, 80 ° and 100 ° C) used in drying in a bed-fixed dryer, as well as to evaluate the effects of natural drying, sun and intermittent drying on an industrial scale on the main parameters of evaluation of the quality of these grains during 12 months of storage. The results obtained in the second study indicate that the use of high temperatures in drying causes physiological disturbances and causes negative changes in the chemical, physical, industrial and cooking parameters of the grains. The bioactive compounds are adversely affected in the beans subjected to drying at a temperature of 100 ° C. The use of temperatures equal to or less than 60 ° C better preserved the nutritional value and the industrial and cooking qualities of the grains.